This invention relates to tuning means for tuning stringed instruments, a guitar comprising tuning means and a method of tuning stringed instruments, particularly but not exclusively relating to electric guitars.
The sound produced by a musical instrument may be considered to be made up of two elements, namely a pitch or note, and a quality which is characteristic of the type of instrument being played. Differences in quality are easily discernable to the human ear, for example the sound of a piano and a violin playing the same note. These differences in quality are due to the differences in the complex mixtures of harmonics which result from the construction of the instrument, whilst the fact that the human ear identifies two notes as the same despite being played on different instruments is due to the fundamental frequency (of which the harmonics are multiples) being the same.
Evolutionary improvements in design have resulted in instruments which, at least over a short period of time such as a practice session or concert, reliably produce the same pitch and quality of sound at the behest (and sometimes the skill) of the player. Due to changes in temperature or humidity however, or other physical change perhaps due merely to age or use, an instrument may not necessarily produce the same pitch over a longer period, say from day to day.
In western music notation, the audible range of frequencies is divided up into octaves, the frequency of any note being double that of an octave below it. An octave is divided into twelve notes separated in frequency by equal logarithmic steps, called semi-tones, and these twelve notes are divided into a group of seven natural notes, identified by the first seven letters of the alphabet, and a group of five notes, identified by their position relative to the other seven, either being the next higher semitone (sharp) or the next lower semitone (flat).
It is desirable that an instrument can be adjusted so that the note produced as a result of any given input from the player can be altered to a different setting, usually over a small range. Principal reasons for this are that the trained ear is accustomed to a given identified note actually producing a given frequency; or to ensure that different notes produced on the same instrument bear the correct relationship to one another; or to ensure that several instruments when played in concert produce exactly the same frequencies for the same notes. If this were not the case, an unpleasant sound would result, due to the production of beat frequencies. This process of adjusting the output pitch or frequency from the instrument is known as tuning.
Many instruments such as those of the brass or woodwind family are capable of playing only one note at a time from within the instrument""s range, the relationship between the notes available being dictated essentially by the physical manufacture of the instrument, and the possibilities for tuning being limited to finely adjusting the entire range together. Other instruments notably those of the string family, and keyboard instruments, have several or even a multiplicity of individually tuned components. The tuning process for these instruments therefore involves bringing to the correct relative pitch each individual tuned component of the instrument. The pitch of the note produced by a string depends on its physical qualities of material and construction, its length, and its tension; and since in most cases the strings themselves, and the tuned lengths, are not changed in the tuning process, the only variable altered is the tension.
For reasons of weight, appearance, and the desire that the structure of the instrument itself contributes to the quality of the sound produced, commonly the structural stiffness of the instrument is such that the tension of the strings produces a detectable deflection in the structure. Consequently, adjustment of the tension of any one string alters the stresses on the instrument""s structure, thereby altering its stressed shape, and thereby affecting the tuning of the other strings. In other words, tuning of any one string is not independent of the tuning of the others, and increasing the tension in one string to increase its pitch will result in the remaining strings having reduced tension, and vice versa. This is why an iterative tuning procedure is required, whereby the player tunes each string in turn, perhaps several times, even if the cause was that only a single string was out of tune.
Electric guitars fitted with a vibrato device are particularly affected by this phenomenon. In these instruments the tail end of the strings are anchored in a bridge plate which is free to pivot about its front edge. The tension of the strings tending to rotate the bridge plate in one direction is opposed by the tension in one or more springs located within the guitar body, and the bridge plate therefore assumes an equilibrium position where the resulting torques are balanced. Movement of the vibrato arm by the player thus moves the bridge plate away from the equilibrium position, generally reducing the tension in the strings and resulting in the characteristic sound effect. Upon release of the lever, the bridge plate resumes its equilibrium position and correct tuning is restored, depending on the absence of friction. It is obvious that any alteration in tension in any string alters the equilibrium position of the bridge plate, and therefore alters the pitch of the other strings.
It is an aim of the present invention provide a new or improved tuning means for a stringed instrument.
According to a first aspect of the invention we provide a tuning means for a stringed instrument having one or more strings comprising actuating means to vary the tension of the or each string.
The tuning means may comprise detection means to provide a signal in response to vibration of the or each string and analysis means to control said actuating means in response to said signal
The actuating means may comprises a motor, which may be a DC motor.
The actuating means may comprise a gearbox.
The gearbox may be connected between said motor and a string.
The gearbox may be an epicyclic gearbox and may comprise six epicyclic stages.
The gearbox may have a reduction ratio in the range 2000:1 to 20000:1.
The analysis means may comprise a first filter means.
Said first filter means may comprise one or more filters.
Said first filter means may comprise a reconfigurable digital band pass filter.
The analysis means may comprise an analogue to digital converter to convert said signal to a digital signal before said signal is passed to said first filter.
The analysis means may further comprise a second filter means, said second filter means comprising an analogue band pass filter to filter the signal before said signal is passed to said first filter.
The analysis means may have at least one of an operating mode wherein the analysis means operates said actuating means in response to said signal, and an operating mode wherein the analysis means operates a visual display showing the tuning of each string in response to said signal. The operating modes may be selectable by an operator.
The visual display means may comprise a light emitting diode, which shows a first colour if the frequency of the string is above a desired frequency range, and a second colour if the frequency of the string is below a desired frequency range.
The tuning means may be operable to tune the or each string to a desired accuracy, preferably to within xc2x10.02 of a semitone.
Where the string instrument has a plurality of strings, said tuning means may be operable to perform a plurality of tuning cycles wherein each string is tuned in turn. Alternatively, the strings may be tuned simultaneously in each tuning cycle.
According to a second aspect of the invention we provide a guitar having a plurality of strings and comprising tuning means according to the first aspect of the invention.
The detection means may comprise a pick up provided on said guitar.
The pick up may comprise a coil responsive to all of the strings, or alternatively may comprise a plurality of coils each responsive to one of said strings.
Where the actuating means comprises a motor or a motor and a gearbox, the strings may be connected at one end to a bridge plate, said bridge plate being pivotally attached to the guitar and moveable to vary the tension of the strings, a mechanical block being provided attached to and pivotal with said bridge plate, said block housing said motor or said motor and said gearbox.
According to a third aspect of the invention, we provide a method of tuning a stringed instrument having one or more strings comprising operating an actuating means to vary the tension of the or each string.
The instrument may comprise a plurality of strings, each of said strings being initially tuned to within a preset frequency range, wherein the instrument comprises tuning means comprising a detection means to provide a signal in response to vibration of one or more of said stings, actuating means to adjust the tension of said strings operable by an analysis means in response to said signal, the method comprising the steps of causing all of the strings of the instrument to vibrate and performing a tuning cycle comprising measuring the frequency of vibration of one of said strings, operating said actuating means to adjust the tension of said one string to vary said frequency of said one string and repeating said process for each of said strings.
The method may comprise performing a plurality of said tuning cycles.
Each tuning cycle other than the first of said plurality of tuning cycles may comprise the further step of measuring the change in said frequency of said one string in response to operation of said actuating means in the preceding tuning cycle and varying the operation of said actuating means accordingly.
Where the analysis means comprises a reconfigurable filter, the method may further comprise the step of setting said reconfigurable filter to have a centre frequency corresponding to a desired frequency of one of said strings and a width corresponding to said frequency range.
Where one or more of said strings are initially outside said preset frequency range said method may comprise the prior steps of causing one of said one or more strings to vibrate, setting said filter to have a centre frequency and increasing said centre frequency to identify the frequency of said one string, and providing a visual indication of the tuning state of said string.
The tuning means may comprises a tuning means according to the first aspect of the invention.
The stringed instrument may comprise a guitar according to the second aspect of the invention.